Preheat oven to 350 degrees F. Line muffin tins with cupcake liners (12 regular, 48 mini, or a combo of 6 regular and 24 mini).
In a mixing bowl, combine flour, baking powder, baking soda, and salt.
In another bowl, melt butter and whisk in the sugar, buttermilk, sour cream, and vanilla. Add the liquid ingredients to the dry and mix until just combined. Set aside.
With an electric mixer, beat egg whites until soft peaks form. Fold into the batter until combined.
Spoon batter into cupcake liners (I like to use an ice cream scoop for the regular size cupcakes and a cookie scoop for the mini). Bake mini cupcakes for 9-11 minutes and regular cupcakes for 15-18 minutes until toothpick comes out clean. (If you are baking mini and regular cupcakes, bake the mini ones first and then the regular.)
For the Frosting
Melt the chocolate in the microwave on low in 20 second increments, stirring after each. Let the chocolate cool slightly for about 2-3 minutes so it is not too hot that it melts the butter and cream cheese.
In a mixing bowl, beat butter and cream cheese on medium speed for 1 minute. Add the melted chocolate and vanilla and beat anther minute. Beat in the sugar a little at a time, mixing until until light and fluffy. Add milk 1 tablespoon at a time if needed to reach desired consistency. Place in a piping bag with tip and pipe onto the cupcakes.
For the Coconut Egg Nests
Preheat oven to 300 degrees. Spread out coconut on cookie sheet in a single layer and place in oven. Pull out sheet and stir coconut around and place back in oven in 5 minute intervals until completely toasted and browned.
Microwave white chocolate chips in 30 second intervals until melted. Slowly add in toasted coconut to the melted chocolates until combined, making sure not to add all the coconut as it needs a good layer of chocolate to adhere.
Drop spoonfuls of chocolate coconut mixture on wax paper, pressing down in the middle to create “nest” shape. Place a few candies of choice in the center to resemble eggs. Let harden in fridge for 10 minutes before removing and displaying on plate.